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Power Line Circuits
Last Updated on:
Monday, October 03, 2011 06:07 PM |
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| Circuits
Designed by Dave Johnson, P.E. : |
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ISOLATED AC CURRENT MONITOR
This circuit uses a small AC current transformer from Magnetek to produce an
isolated voltage proportional to the AC current in the primary winding....
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Miniature 5v Line Powered Isolated Supply
Often a circuit requires a 5v DC supply to power some logic circuits. The
conventional method is to use an AC wall adapter. But, many systems, which
bring AC power onto a circuit board, need a small AC to DC power supply right on
the circuit board. The circuit below provides such a supply. It uses
a classic series capacitor charge pump which acts as a current limiting device.
A full wave rectifier, a filter capacitor and a zener diode provide an
off-the-shelf isolated DC to DC converter with a 24v DC input. The
miniature converter from CUI generates a regulated +5v output, rated at 100ma.
By doubling the size of the capacitor C1 the circuit can be pushed to produce
200ma of output current. Also, the same front end circuit can be used with
other CUI converters. They sell 3.3v, 12v and 15v supplies as well as the
5v unit shown.
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UNPLUGGED POWER CORD ALARM
Many medical devices, such a portable X-ray and ultrasound equipment, carry
their own batteries. However, the frantic pace of some hospital emergency rooms
might cause the device to be shoved off into a corner without being plugged...
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Unplugged Appliance Alarm
I got a call from an administrator at a
large prison. He told me that he was having problems with inmates who keep
unplugging refrigerators, vending machines and microwave ovens...
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Links to electronic
circuits, electronic schematics, designs for engineers, hobbyists, students &
inventors:
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220 Volt Live Wire in Wall Scanner - This little circuit will
help you to scan line of a 220V live wire in wall. FET gate
is connected to a capacitive metal sensor (which is usually a simple
metal plate). When you hold sensor close to wall, LED
will indicate current flow around where it detects wire.
Works on 9VDC.... [Peter Jakab, Electrical Engineer, Engineer of
Informatics] |
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3˝ Digit DVM IC Measures Power Factor - 04/28/94 EDN-Design
Ideas....Circuitry in Fig 1 allows ICL7106/7107] digital-voltmeter
IC, IC4, to measure power factor to0.1% resolution and operate from a
single 9Vdc supply. An important feature of circuit is that
variations in load current, line voltage,.... [Design Idea by Devadoss
John and KRS Sarma, Hindustan Cables Ltd, Hyderabad, India] |
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Ac Line Powered LED Pilot Light - This simple circuit can be
used to light a LED indicator lamp, powered from the 120vac line.
I have included component values for 240vac lines as well.. [Designed by
David A. Johnson] |
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AN-872: TP3420A Line Interface Circuit Considerations -
National Semiconductor Application Note....[App Note] |
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Calculating Power Dissipation for Differential Line Drivers -
National Semiconductor Application Note (app note added 2/06)
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Isolated AC Current Monitor - This circuit uses a small AC current
transformer from Magnetek to produce an isolated voltage proportional to the AC
current in the primary winding. The transformer contains a single turn
primary with a low 0.001-ohm resistance. It can easily handle 30 amps of AC
current and provides at least 500vac of isolation. With the components
shown, the output AC voltage is scaled so 1 amp of current produces 100mv of AC
voltage.... [Designed by David A. Johnson] |
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Line Powered 60hz Clock Generator - This circuit is connected to the
120vac power line and transfers 60Hz clock pulses to a logic circuit. The
optoisolator used provides 5000 volts of isolation between the power line and the
logic side of the circuit.... [Designed by David A. Johnson] |
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Line Powered White LED Array - There has been a lot of excitement
lately in the lighting industry. Some companies are beginning to manufacture
general lighting fixtures, which replace incandescent and fluorescent lamps, using
LED lights. When proper heat management is designed into the light fixtures,
these LED lights can produce more light with less electricity and last much longer
than other devices. They can also operate well in cold temperatures.
Some of these new lighting fixture designs use a large number of white LEDs, wired
into long series wired string arrays. The circuit below is designed to
provide a regulated DC voltage for these strings. [Designed by David A.
Johnson] |
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Line Powered Xenon Flash Transmitter - This line powered xenon flash
circuit drives a small camera type flash tube. It has an optical isolator to allow
the flash to be safely triggered from some remote device. A flash rate of 2Hz is
possible with the circuit. …. [Designed by David A. Johnson] |
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Miniature 5v Line Powered Isolated Supply - Often a circuit requires a
5v DC supply to power some logic circuits. The conventional method is to use
an AC wall adapter. But, many systems, which bring AC power onto a circuit
board, need a small AC to DC power supply right on the circuit board. The
circuit below provides such a supply. It uses a classic series capacitor
charge pump which acts as a current limiting device. .... [Designed by David A.
Johnson] |
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Off Line Power Supply Requires Few Parts - 02/17/94 EDN-Design IdeasThis
simple non-isolated off-line power supply can provide up to150 mA5V and uses only
a handful of components from110-230-Volt AC input voltage. Note that the low
voltage output is directly connected to the mains; it cannot be used when the low
voltage part can be touched.... [Design Idea by Sam Ochi, IXYS Corp, Santa Clara,
CA] |
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Unplugged Appliance Alarm - I got a call from an administrator at a
large prison. He told me that he was having problems with inmates who keep
unplugging refrigerators, vending machines and microwave ovens in a commons area.
He wanted a battery-powered device, which could be mounted to the outside of the
power cord of an appliance. The device would produce a loud alarm whenever
the power plug of the appliance was unplugged from a power outlet.... [Designed by
David A. Johnson] |
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Unplugged Power Cord Alarm - Many medical devices, such a portable
X-ray and ultrasound equipment, carry their own batteries. However, the frantic
pace of some hospital emergency rooms might cause the device to be shoved off into
a corner without being plugged back into an AC power source to recharge their
batteries. So, I designed this circuit to emit an audible alarm whenever the
device’s power cord was unplugged from the wall for a period of time. The device
was designed to snap onto the outside of a power cord, where it senses the AC
electric field emitted. No direct connection to the internal wires of the power
cord is needed. I also included a low battery voltage monitor.... [Designed by
David A. Johnson] |
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